Do we need a concept of disease?

The terms “health”, “disease” and “illness” are frequently used in clinical medicine. This has misled philosophers into believing that these concepts are important for clinical thinking and decision making. For instance, it is held that decisions about whether or not to treat someone or whether to relieve someone of moral responsibility depend on whether the person has a disease. In this paper it is argued that the crucial role of the ‘disease’ concept is illusory. The health/disease distinction is irrelevant for most decisions and represents a conceptual straightjacket. Sophisticated and mature clinical decision making requires that we free ourselves from the concept of disease.     

Conscious thought as simulation of behaviour and perception

A 'simulation' theory of cognitive function can be based on three assumptions about brain function. First, behaviour can be simulated by activating motor structures, as during an overt action but suppressing its execution. Second, perception can be simulated by internal activation of sensory cortex, as during normal perception of external stimuli. Third, both overt and covert actions can elicit perceptual simulation of their normal consequences. A large body of evidence supports these assumptions. It is argued that the simulation approach can explain the relations between motor, sensory and cognitive functions and the appearance of an inner world.     

Cerebellum and conditioned reflexes

The central assumption of existing models of motor learning in the cerebellum is that cerebellar mossy fibres signal information about the context in which a movement is to be performed and climbing fibres signal in relation to a movement error. This leads to changes in the responsiveness of Purkinje cells, which on the next occasion will generate a corrected output in a given context. Support for this view has come mainly from work on adaptation of the vestibulo-ocular reflex. The discovery that classically conditioned eyeblink responses depend critically on the cerebellum offers the possibility to study the learning of a novel behaviour, rather than modification of an existing reflex. After repeated pairing of a neutral stimulus, such as a tone, with a blink-eliciting stimulus, the tone will acquire the ability to elicit a blink on its own. We review evidence from studies employing a wide variety of techniques that the cerebellum is critical in this type of learning as well as evidence that mossy and climbing fibres have roles assigned to them in cerebellar learning models.